In the past, Korea had many kinds of jeupjang (succulent jang), a rapidly maturing original Korean jang (fermented soybean paste) of which there is no record in Chinese cookbooks. However, this local delicacy has almost been forgotten. Therefore, we looked for information about jeupjang in cookbooks written prior to the Joseon Dynasty in Korea (1392~1910) and in the 1950s. Among the recipes, there were 34 jeupjangs prepared with vegetables, such as eggplant and cucumber, and 9 without. The main ingredients of jeupjang are soybean, bran (wheat crust), and barley, and wild wheat is also used. Jeupjang is made in small portions to expedite its rapid maturation, but the most common form is egg-shaped, and there is also a flat or round, hilt-shaped version. In most cases, jeupjang consists of a mixture of meju powder (moldy soybean), water, and salt. Other ingredients can include nuruk (moldy bran), bran, wheat flour, an alcoholic beverage, maljang (dried fermented soybeans), ganjang (liquid soy sauce), malt, and takju (Korean murky wine). Jeupjang meju can be fermented in a vessel, most widely in baskets made of straw (sum and dungumi) or willow or interwoven twigs (chirung), but jars can also be used. The leaves of the paper mulberry are generally used for the mat and cover, but straw or leaves of the sumac, mulberry, or pine tree, soy, and fallen leaves are also used. Unlike other jangs, jeupjang is matured at $60^{\circ}C$ to $65^{\circ}C$, using heat emitted from the decomposition of horse dung, haystacks, or manure. Jeupjang became defunct or was transformed into jeomjang, jiraejang, mujang, paggeumjang, makjang, jipjang, and tojang. These jangs differ from jeupjang in that they use rice, malt, or hot pepper powder.